Optical isotope shift measurements using collinear ion beam laser spectroscopy and the configuration of the NdII(23537) 9/2 0 level

The optical isotope shifts of five even isotopes of neodymium have been measured by using collinear ion beam laser spectroscopy (CIBLS). Isotopically pure NdII ions with energy of 30ke V from an isotope separator were collinearly interacted with light from a tunable dye laser and selectively excited from a metastable level of 4f4 5d6 K9/2 to the (23537)9/20 level by Doppler tuning technique. The resonant excitation frequency values for each Nd isotope with mass number of 142, 144, 146, 148 and 150 were obtained. After the separation of the normal and specific mass shift and the field shift from the experimentally measured isotope shift, the configuration of the (23537)9/20 level was decomposed into 4f4 6p, 4f3 5d2 and 4f3 5d6p, and their fractions, for the first time. were determined to be 0.12-0.13, 0.88-0.85 and 0-0.02, respectively.